Dynamic subchannel and bit allocation in multiuser MIMO/OFDMA systems

An adaptive subchannel allocation and modulation scheme is developed for multiuser multiple-input multiple-output (MIMO)/orthogonal frequency division multiple access (OFDMA) systems through some modification of the approach for OFDMA systems. In the multiuser MIMO/OFDMA system, there are SDMA subchannels, in which each user occupies a single-user MIMO subchannel, for each OFDM subcarrier. An optimal procedure for allocating the SDMA subchannels to users and loading bits to single-user MIMO subchannels is formulated as an integer programming (IP) problem. Then, a suboptimal algorithm that separately performs subchannel allocation and bit loading is proposed. Computer simulation results indicate that the performance of the suboptimal algorithm is reasonably close to that of the optimal IP.